Thermoplastic (fibre reinforced) polymers, including oligomers are increasingly used as a construction material because it offers the possibility for recycling. A thermoplastic polymer can be heated to soften it (amorphous thermoplastics) or to ultimately melt it (semi-crystalline thermoplastics), and then cooled to return it to its solid state. Such temperature-induced physical changes are generally reversible which makes thermoplastic polymers recyclable. In solid amorphous thermoplastics the polymer molecular chains are arranged in a random fashion, whereas in solid semi-crystalline thermoplastics some portions thereof comprise polymer molecular chains arranged in an orderly fashion: the crystalline regions. The invention is not limited to one type of thermoplastic polymer, even if the wording ‘melting’ or ‘melt’ is used. Thermoplastic polymers exhibit a glass transition temperature (Tg) above which, with further heating, progressive softening occurs. At temperatures substantially higher than the glass transition temperature, amorphous thermoplastics behave like a high viscosity liquid, whereas semi-crystalline polymers are still solid in this temperature region. Semi-crystalline thermoplastics exhibit a melting temperature (Tm), above which the material melts and behaves as a liquid. With further increases in temperature the viscosity falls off quickly.
Thermosetting polymers are typically cross-linked polymers that comprise resins such as epoxide (often called epoxy), bismaleimide, unsaturated polyester and vinylester polymers. A thermosetting polymer typically comprises prior to curing a resin (a monomer) and a hardener, which react together to produce a cross-linked polymer. Curing may be designed to occur at room temperature or at higher temperatures, which typically ranges between 80 and 200° C. During curing, the monomer and hardener react and the viscosity of the mixture increases until it becomes a cross-linked solid polymer, which state is not reversible by a temperature change, unless the thermosetting polymer is degraded at a temperature above its degradation temperature. After curing, a thermosetting polymer also exhibits a glass transition temperature, above which considerable softening of the thermosetting polymer occurs and the thermosetting polymer behaves like a rubber.
Polymer composite materials comprise a fibre or particulate reinforcement embedded in a matrix polymer, which can be either thermosetting or thermoplastic. Well-known polymer composites include glass fibre reinforced polyester resin, and carbon fibre reinforced epoxy. Both these composites use thermosetting polymers as the matrix, and are therefore often called thermosetting composites.
One major drawback of thermosetting (composite) polymers is that they are generally not weldable, since a thermosetting polymer cannot be melted and resolidified by raising and lowering the temperature. Thermosetting (composite) polymers are typically adhered to other components by adhesive bonding or bolting, both of which have disadvantages. Adhesive bonding is costly, sometimes hazardous to the environment, and the quality of bonding achieved is generally sensitive to variations in process parameters. Bolting on the other hand produces holes in the components to be bonded, which gives rise to stress concentrations and premature failure possibly.
It would be desirable to provide a wider range of thermosetting polymers or thermosetting polymer composites with the possibility to bond them by welding to another thermosetting polymer or thermosetting polymer composite or to a thermoplastic polymer (composite).
The present invention provides a method for bonding a thermosetting polymer (composite) component to another thermosetting polymer component by providing the thermosetting polymer (composite) with an thermoplastic implant, which offers a thermally bondable surface.
The invention further provides a cured thermosetting polymer component comprising an implant of a thermoplastic polymer at least at the part of the thermosetting polymer component to be bonded, as well as an uncured or partly cured thermosetting polymer component having an implant of a thermoplastic polymer that forms a bondable surface.
The invention also provides an assembly of a cured thermosetting polymer component with a thermoplastic surface and a thermoplastic polymer.
The present invention further provides an uncured or partly cured thermosetting polymer component having an implant of a thermoplastic polymer (component) that forms a thermally bondable surface, and an assembly of a cured thermosetting polymer component with a thermoplastic surface and a thermoplastic polymer component welded thereto.